BACKUP POWER
How Long Can a Battery Run a Refrigerator and Freezer?
Estimate refrigerator and freezer battery runtime from measured kWh, usable capacity and inverter losses.
Runtime equals usable battery watt-hours multiplied by inverter efficiency, divided by the appliances’ average watts. A 2,000 Wh battery with 85% usable energy and 90% conversion efficiency provides about 1,530 Wh; at a combined 150-watt average load, that is roughly 10 hours.
- ✓ Use average energy for runtime
- ✓ Verify surge for compressor startup
- ✓ Account for usable capacity and losses
The runtime formula
Estimated hours = battery nameplate Wh × usable fraction × inverter efficiency ÷ average load watts. Use measured average watts or daily kWh where possible because compressors cycle.
The example above is an estimate, not a guarantee. Battery temperature, age, inverter standby use and refrigerator cycling change the result.
Measure both appliances
Monitor each appliance over a representative 24–72 hours. Add their daily kWh, convert to average watts by dividing Wh by 24 hours, and make sure the inverter can handle simultaneous compressor surge.
- Include automatic defrost cycles
- Avoid opening doors during an outage
- Pre-cool before forecast outages when safe
- Keep food-safety guidance available
Add reserve and a recharge plan
Do not plan to use every nameplate watt-hour. Use the manufacturer’s usable-capacity guidance, include a reserve and decide how the battery will recharge. Solar recharge should be based on realistic daily production and input limits.
Actual energy use and product performance vary by equipment, conditions and installation. Confirm measurements and manufacturer specifications. Qualified professionals should handle permanent wiring and transfer equipment.